The number of persons in the tax household is obtained by adding up the persons listed on the income declarations of the said household. The term person is used rather than inhabitant to highlight the fact that a person attached in tax terms to a household does not necessarily live in it: they may live elsewhere, as is frequently the case of students (attached to their parents for tax purposes but living in a separate dwelling).
For these particular reasons, the number of persons is not always the same as the population of the household in the population census. Differences can therefore be observed between the numbers from the two sources.
Since the 2003 tax return, children and grand-children subject to alternating custody arrangements have been taken into account. They are counted as 0.5 in each of the two dwellings where they reside.